Algebra
posted by Tori .
You have 600 feet of fencing to enclose a rectangular plot that borders on a river. If you do not fence the side along the river, find the length and width of the plot that will maximize the area. What is the largest area that can be enclosed?

area= LW
but 2W+L=600
L= 6002W
area= (6002W)(w)
well, roots are w=0, and w=300 that is where area is zero. Since a parabola is described here, the max will occur halfway, or w=150. Solve for Area when w=150
Plot Area vs W and see if this is so. Use your graphing calculator. 
I already know that the answer is 300 for the length and 150 for the width, giving a sq ft of 45,000. The only problem is i do not know how to get that answer.

@bobpursley i got it now. thanks a bunch =)